· Web viewBy 2050, India is predicted to pass it. Pakistan is projected to become 3rd with Iran and Ethiopia following. Pakistan is projected to become 3rd with Iran and Ethiopia

HUMAN POPULATION DYNAMICS

Chapter Overview Questions What is the history of human population growth, and how many people are likely to be

here by 2050? How is population size affected by birth, death, fertility, and migration rates? How is population size affected by percentages of males and females at each age level? How can we slow population growth? What success have India and China had in slowing population growth? What are the major impacts of human activities on the world’s natural ecosystems?

Core Case Study: Is the World Overpopulated? The world’s population is projected to increase from 6.6 billion to 8.9 billion between

2006 and 2050. The debate over interactions among population growth, economic growth, politics, and

moral beliefs is one of the most important and controversial issues in environmental science.

Much of the world’s population growth occurs in developing countries like China and India.

Some argue that the planet has too many people. Some feel that the world can support billions of more people due to technological

advances. There is a constant debate over the need to reduce population growth.

o Must consider moral, religious, and personal freedom.

HUMAN POPULATION GROWTH: A BRIEF HISTORY The human population has grown rapidly because of the expansion of agriculture and

industrial production and lower death rates from improvements in hygiene and medicine.o In 2006, the population of developed countries grew exponentially at 0.1% per

year. o Developing countries grew (15 times faster at 1.5% per year).

Where Are We Headed? We do not know how long we can continue increasing the earth’s carrying capacity for

humans. There are likely to be between 7.2-10.6 billion people on earth by 2050. 97% of growth in developing countries living in acute poverty. What is the optimum sustainable population of the earth based on the cultural carrying

capacity? U.N. world population projection based on women having an average of 2.5 (high), 2.0

(medium), or 1.5 (low) children.

FACTORS AFFECTING HUMAN POPULATION SIZE Population increases because of births and immigration and decreases through deaths and

emigration.

Instead of using raw numbers, crude birth rates and crude death rates are used (based on total number of births or deaths per 1,000 people in a population).

Age Structure: Young Populations Can Grow Fast

How fast a population grows or declines depends on its age structure. Prereproductive age: not mature enough to reproduce. Reproductive age: those capable of reproduction. Postreproductive age: those too old to reproduce.

Limits on Population Growth: Biotic Potential vs. Environmental Resistance

No population can increase its size indefinitely.o The intrinsic rate of increase (r) is the rate at which a population would grow if it

had unlimited resources.o Carrying capacity (K): the maximum population of a given species that a

particular habitat can sustain indefinitely without degrading the habitat.

Exponential and Logistic Population Growth: J-Curves and S-Curves Populations grow rapidly with ample resources, but as resources become limited, its

growth rate slows and levels off. As a population levels off, it often fluctuates slightly above and below the carrying

capacity.

Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size

Over time species may increase their carrying capacity by developing adaptations. Some species maintain their carrying capacity by migrating to other areas. So far, technological, social, and other cultural changes have extended the earth’s

carrying capacity for humans.

Population Density and Population Change: Effects of CrowdingPopulation density: the number of individuals in a population found in a particular area or volume.

o A population’s density can affect how rapidly it can grow or decline. e.g. biotic factors like disease

o Some population control factors are not affected by population density. e.g. abiotic factors like weather

Reproductive Patterns:Opportunists and Competitors Large number of smaller offspring with little parental care (r-selected species). Fewer, larger offspring with higher invested parental care (K-selected species). r-selected species tend to be opportunists while K-selected species tend to be competitors.

Many small offspring

Little or no parental care and protection of offspring

Early reproductive age

Most offspring die before reaching reproductive age

Small adults

Adapted to unstable climate and environmental conditions

High population growth rate (r)

Population size fluctuates wildly above and below carrying capacity (K)

Generalist niche

Low ability to compete

Early successional species

r-Selected SpeciesCockroachDandelion

Survivorship Curves: Short to Long Lives

The populations of different species vary in how long individual members typically live.

Fewer, larger offspringHigh parental care and protection of offspringLater reproductive ageMost offspring survive to reproductive ageLarger adultsAdapted to stable climate and environmental conditionsLower population growth rate (r)Population size fairly stable and usually close to carrying capacity (K)Specialist nicheHigh ability to competeLate successional species

K-Selected Species

SaguaroElephant

FACTORS AFFECTING HUMAN POPULATION SIZE Average crude and birth rates for various groupings of countries in 2006.

FACTORS AFFECTING HUMAN POPULATION SIZE The world’s 10 most populous countries in 2006 with projections in 2025.

14

Europe

North America

UnitedStates

OceaniaAsia

AfricaLatin and

Central America

381521

620

7177

1488

1110

Declining Fertility Rates: Fewer Babies per Women The average number of children that a woman bears has dropped sharply. This decline is not low enough to stabilize the world’s population in the near future.

o Replacement-level fertility: the number of children a couple must bear to replace themselves.

o Total fertility rate (TFR): the average number of children a woman has during her reproductive years.

Case Study: Fertility and Birth Rates in the United States Nearly 2.9 million people were added to the U.S. in 2006:

o 59% occurred because of births outnumbering deaths.o 41% came from illegal and legal immigration.

In 2006, the total fertility rate in the United States was slightly > 2.0

Average crud

e death rate

Average crud

e birth rate

World 219

All developedcountries

1110

All developingcountries

278

9

23

Developingcountries

(w/o China) 2025

1.5 billionChina 1.3 billionIndia 1.1 billion1.4 billionUSA 300 million349 millionIndonesia225 million264 millionBrazil187 million229 millionPakistan166 million229 millionBangladesh147 million190 millionRussia142 million130 million

135 millionNigeria199 millionJapan121 million128 million2006

ReplacementLevel

YearBirt

hs p

er w

oman

Baby boom(1946–64)

o The baby bust that followed the baby boom was largely due to delayed marriage, contraception, and abortion.

Factors Affecting Birth Rates and Fertility Rates The number of children women have is affected by:

o The cost of raising and educating them.o Availability of pensions.o Urbanization.o Education and employment opportunities.o Infant deaths.o Marriage age.o Availability of contraception and abortion.

Factors Affecting Death Rates Death rates have declined because of:

o Increased food supplies, better nutrition.o Advances in medicine.o Improved sanitation and personal hygiene.o Safer water supplies.

U.S. infant mortality is higher than it could be (ranked 46th world-wide) due to: Inadequate pre- and post-natal care for poor. Drug addiction. High teenage birth rate.

Case Study: U.S. Immigration Since 1820, the U.S. has admitted almost twice as many immigrants and refugees as all

other countries combined.POPULATION AGE STRUCTURE

47 years

Homicides per100,000 people

Hourly manufacturing job wage (adjusted for inflation)

Living insuburbs

Homes withelectricity

Homes withflush toilets

High schoolgraduates

Married women workingoutside the home

Life expectancy

1.2 5.8$15$352%10%

99%2%98%10%

83%15%81%

20001900

8%77 years

The number of people in young, middle, and older age groups determines how fast populations grow or decline.

The number of people younger than age 15 is the major factor determining a country’s population growth.

Changes in the distribution of a country’s age groups have long-lasting economic and social impacts.

Populations with a large proportion of its people in the preproductive ages 1-14 have a large potential for rapid population growth.

32% of the people in developing countries were under 15 years old in 2006 versus only 17% in developed countries.

POPULATION AGE STRUCTURE Today, baby boomers make up nearly half of all adult Americans and dominate the

populations demand for goods and services.PARTS

Broken down by age. You can see the birth rate, maturity rate and death rate of an entire population. Usually broken down by country.

Expansive/rapid growth Birth rate exceeds the death rate. Population is getting larger. Pyramid shaped

histogram. Ex’s. Kenya, Nigeria and Saudi Arabia.

Stable/Slow Growth (Zero Growth) Birth rate almost equals death rate. The population is not getting any larger or is growing

very slowly. Histogram shape is straighter and more box-like until about age 45-85. Ex. US, Australia & Canada has slow Denmark, Austria and Italy has stable

Declining (negative growth) When the birth rate is smaller than the death rate. The pyramid bulges near the top or is

inverted. Ex. Germany, Bulgaria & Hungary.

Demography: The study of human populations, their characteristics and changes.

Population Explosion Anything that causes the population to grow uncontrollably. (Read Miller’s pg 175 &

180) Ex. Baby boom. 78 Million person increase between 1946-1964. Look at the histogram on pg 180.

Exponential Growth Growth of a population that increases by a fixed percentage of the whole in a give time. When plotted it looks like the letter J.

Thomas Malthus (Miller Pg. 173) “diminishing returns” He argues that rising wages and improved well-being would lead to excess reproduction

among the working class. A labor surplus would then cause wages to fall below subsistence levels, resulting in

starvation, disease and crime. In his view, land for food production was the limiting factor in both population growth

and economic development. Biotic Potential

Maximum reproductive rate of an organism. Of course there are limiting factors for a population. For example the common housefly can lay 120 eggs in each generation. If nothing hurt

the eggs or the flies, in 7 generations there would be 6,182,442,727,320 flies.

Human predictions If there was a continued growth and not death, food would run short and available space

would run out. But, humans can’t reproduce as fast as other animals. This helps to stop the growth.

Demographic Measures Statistics about people, such as births, deaths, and where they live as well as total

population size. Density- number of people in a certain space.

Birth rate(natality)- the number of births in a year per 1,000 people.

Death Rate (mortality)- the number of deaths in a year per 1,000 peopleGrowth Rate- includes birth rate, death rate, immigration and emigration Doubling time- The time it takes for the population to double the number of peopleGross National Product- The most commonly used measure of the economic growth of a country.Immigration- People coming into the population

Emigration- The movement of people out of the population.

Net Migration- Total number of people moving into or out of the population. Infant mortality rate- Number of child/infant deaths. If a mother lives in an area with a high infant mortality rate she will tend to have a lot of children to ensure some will make it to adulthood. Zero Population Growth- When the number of births, equals the number of deaths. No growth in the population.

Total Fertility Rate- an estimate of the average number of children a women will have during her childbearing years. Replacement-level fertility- the number of children a couple must bear to replace themselves. It is slightly higher than two children per couple. (2.2 in developed countries and as high as 2.5 in some developing countries)It is greater in countries w/ high infant mortality rates than in countries w/ low infant mortality ratesAge structure- Percentage of the population at each age level in a population

Generation time- the time it takes for 1 generation to pass.

Growth rate (Birth rate-death rate) + (immigration – emigration) / 10 If a population of 10,000 experiences 100 births, 40 deaths, 10 immigrants and 30

emigrants in a year, what is the net annual percentage growth rate?

Rule of 70’s 70/ growth rate = doubling time (daily) 72/ growth rate = doubling time (years) If a population of a country grows at a rate of 5% a year, the number of years required for

the pop to double is what?

Demographics of Countries

Developing Countries- China is the largest but has taken drastic population control methods. By 2050, India is predicted to pass it. Pakistan is projected to become 3rd with Iran and

Ethiopia following. However, Russia is losing 600,000 people a year, after being the 4th largest country in

1950. This is because of environmental pollution, hyperinflation, crime, corruption, disease and despair.

SLOWING POPULATION GROWTH IN INDIA AND CHINA For more than five decades, India has tried to control its population growth with only

modest success. Since 1970, China has used a government-enforced program to cut its birth rate in half

and sharply reduce its fertility rate.

India’s Failed Family Planning Program Poor planning. Bureaucratic inefficiency. Low status of women. Extreme poverty. Lack of administrative financial support. Disagreement over the best ways to slow population growth.

China’s Family Planning Program Currently, China’s TFR is 1.6 children per women. China has moved 300 million people out of poverty. Problems:

o Strong male preference leads to gender imbalance.o Average population age is increasing.o Not enough resource to support population.

India’s Failed Family Planning Program

Total fertility rate

PopulationPopulation (2050)

(estimated)Illiteracy (% of adults)

17%20%1.1 billion1.3 billion

1.6 billion

China

GDP PPP per capitaPercentage livingbelow $2 per day

Life expectancy

47%17% 36%20%1.6%0.6%

1.4 billion

$5,890$3,12047 80

70 years62 years27 581.6 children per women (down from 5.7 in 1972)Infant mortality rate

2.9 children per women (down from 5.3 in 1970)

Poor planning. Bureaucratic inefficiency. Low status of women. Extreme poverty. Lack of administrative financial support. Disagreement over the best ways to slow population growth.

Developed countries Usually don’t have such population problems. It can be linked to poverty level even in

developed countries.

SOLUTIONS: INFLUENCING POPULATION SIZE

Demographic Transition: As countries become economically developed, their birth and death rates tend to decline.

o Preindustrial stage: little population growth due to high infant mortality.o Transitional stage: industrialization begins, death rates drops and birth rates

remain high.o Industrial stage: birth rate drops and approaches death rate.

SOLUTIONS: INFLUENCING POPULATION SIZE Generalized model of demographic transition.

o Some developing countries may have difficulty making the demographic transition.

Demographic stages in countries-As countries becomes industrialized their birth rates decline.

Pre-industrial Harsh living conditions lead to a high birth rate and high death rate. Thus, there is little

population growth. Transitional

As industrialization begins, food production rises and health care improves. Death rates drop and birth rates remain high The population grows rapidly

Industrial Industrialization is wide spread The birth rate drops and eventually approaches the death rate.

This is because of: better access to birth control decline in the infant mortality rate increased job opportunities for women

the high cost of raising children who don’t enter the work force until after high school or college.

Postindustrial The birth rate declines even further, equaling the death rate and thus reaching zero

population growth. Then, the birth rate falls below the death rate and the total population size slowly

decreases.U.S. Statistics

Because of the ‘Baby Boom’ the US has a bulge in the pyramid with people in their 50’s-60’s.

There are also more women than men in the older age group because of differences in longevity between the sexes.

Environmental Impact:Environmental Impact Equation (Paul Ehrlich Formula) Population X affluence X technology = Environmental impact

Developed Countries High rates of resource use Result in high levels of pollution and environmental degradation per person These are believed to be the key factors determining overall environmental impact.

Urbanization What happens? Slums, fecal snow, disease This problem doesn’t exist too much in the US because of better working & housing

conditions & air and water quality being improved. Urban areas must import most of its food, water, energy, minerals, & other resources. They produce enormous quantities of wastes that can pollute the air, water & land. 44% of the world’s people live in urban areas that occupy only 5% of the world’s land &

they consume 75% of the world’s resources.

Reasons for World Hunger Issues Unequal distribution of available food Loss of arable land Increasing population growth rate Increasing poverty in developing countries

Reasons the human population has been so dramatic in the last century The Industrial Revolution Modern Medicine

Strategies for ensuring adequate nutrition for a growing population: Increase the number of new food crops from a diversity of plant species Distribute food more equitably Increase land are that is dedicated to grain production rather than meat production Assist developing countries in efficient crop irrigation systems.

Fertility rates & reduction

Environmental pressures of urbanization from population growth are reduced because birth rates in urban areas usually are 3-4 X’s lower than in rural areas.

Cities provide education opportunities. Some countries, including China, penalize couples who have more than one or two children by:

Raising their taxes Charging other fees Eliminating income tax deductions for a couple’s third child Loss of health-care benefits, food allotments and job options

In China couples who pledge to have no more than one child receive

1. Extra food2. Larger pensions3. Better housing4. Free medical care5. Salary bonuses6. Free school tuition for their one child7. Preferential treatment in employment when their child enters the job market.

However, according to some studies, there is a strong preference for male children.1. Girls are aborted at a higher rate than boys2. Some infant girls are killed3. Male children sometimes are fed better than female children.

SOLUTIONS: INFLUENCING POPULATION SIZE Family planning has been a major factor in reducing the number of births and abortions

throughout most of the world. Women tend to have fewer children if they are:

o Educated.o Hold a paying job outside the home.o Do not have their human right suppressed.

SOLUTIONS: INFLUENCING POPULATION SIZE The best way to slow population growth is a combination of:

o Investing in family planning.o Reducing poverty.o Elevating the status of women.

Factors that affect birth & fertility rates Importance of kids in labor force Urbanization Cost of raising & educating kids Availability of private & public pensions Religious beliefs, traditions & cultural norms Educational & employment opportunities

Infant mortality rate Average age at marriage Availability of reliable birth control

1994 Global Summit on Population & Development Cairo, Egypt Encouraged action to stabilized the world’s population at 7.8 billion by 2050, instead of

the projected 11-12.5 billion.

The major goals are to: Provide universal access to family-planning services. Improve the health care of infants, children & pregnant women Encourage development of national population policies Improving the status of women by expanding education & job opportunities Increase access to education for girls Increase men’s involvement in child-rearing responsibility & family planning Take steps to eradicate poverty Reduce & eliminate unsustainable patterns of production & consumption.Annual Rate of Natural Population Change (%)=

Birth rate – Death rate 1,000 people x 100

Declining Fertility Rates: Fewer Babies per Women The replacement level to sustain a population is 2.0 children.

o In 2006, the average global Total Fertility Rate was 2.7 children per woman.o 1.6 in developed countries (down from 2.5 in 1950).o 3.0 in developing countries (down from 6.5 in 1950).

HUMAN ASPECTS ON NATURAL SYSTEMSWe have used technology to alter much of the rest of nature in ways that threaten the survival of many other species and could reduce the quality of life for our own species.